Cable grips for drawing, holding and supporting cables and other flexible conduits, especially electrical cables, are well known in the art. These devices include a tubular body formed from interwoven wire strands which may be expanded radially by endwise compression to enable them to readily receive the cable and radially contracted to frictionally engage the periphery of the cable. Subsequently applied forces tending to separate the grip from the cable cause a firmer grip on the cable. Such open mesh structures in tubular form are readily usable at the end of a cable since they can merely be slipped on to the end.
However, when it is necessary to place a cable grip on a cable at a position distant from the end, a split cable grip is utilized in which the open mesh structure is in the form of a split sleeve with a locking means being provided to close the longitudinal edges forming the split in the sleeve.
Such locking means in the past have included leather thongs, wire lacing, rigid rods or metal clips. An example of such wire lacing is shown in U.S. Pat. No. 3,638,987, issued on Feb. 1, 1972 to Fidrych in which each leg of the lace passes through alternate loops in the mesh structure in a precise under-and-over weaving. In addition, such a locking means can be formed from a rigid pin passing through two series of opposed loops on the longitudinal edges of the split sleeve, as shown in U.S. Pat. No. 2,602,207, issued on July 8, 1952 to Kellems.
Unfortunately, these prior art locking means have significant disadvantages which become especially apparent when viewed in the environment in which the split sleeve cable grips are utilized. In particular, many of these grips are used to support electrical cables extending from the bottom floor to the top floor of a building in which the cable is hung in a shaft provided for such a purpose. Quite commonly, there are a number of such cables, often 10 or 15, which, in larger buildings can extend vertically for more than 1,000 feet. These cables must be supported at various intervals provided by local building codes, such intervals not uncommonly being every 50 feet. Thus, in installing a very long cable in a tall building, more than 10-15 of these cable grips must be installed for each cable.
Typically, the split sleeve is placed about the cable from access areas for the shaft containing the cables. Thus, there is very little room to work with the cable and the split sleeve.
In addition, the manufactured split sleeves are dimensioned so they fit a variety of cable diameters. One particular size split sleeve then must be large enough to fit over the cable when axially compressed but must be small enough so that axial tension will radially reduce the sleeve sufficiently to provide a positive gripping action.
In those situations when the cable diameter is at the maximum width for a given sleeve, there is very little clearance between the inner diameter of the sleeve and the outer diameter of the cable. This complicates closure of the sleeve since there is less "play" between the cable and the sleeve and also requires constant compression of the sleeve about the cable.
Thus, the installing job is time consuming and frustrating to the installer who must meticulously wrap numerous grips in cramped spaces.
It is thus quite obvious that ease of assembly of the cable grip and a permanent connection to the cable are quite important. Leather thongs and wire laces have been found unsatisfactory because it takes considerable time to lace the edges of the grip together and, even when the edges are fully laced, sufficient strength is not always provided to hold the edges of the grip together properly. The metal wire lacing, usually being braided and unresilient, is quite easily kinked and tends to cut the hands of the installer. These laces must be very precisely woven in an under-and-over configuration and it is often the case that impatient installers tend to leave some of the weaving of the loops undone. Moreover, quite often, to provide a proper connection, the operation must be done by two people, one to axially compress the mesh sleeve and the other to weave the lace. If compression is not applied in an adequate amount, the lace is not tight enough and the cable grip can slip. Moreover, in many of these wire mesh cable grips the bottom series of loops are closer together, making the lacing operation at that part very difficult. Complicating all of this is the fact that the cable usually comes from a reel upon which it is initially supported so that the unraveled cable tends to be sinuous and therefore it is difficult to wrap a split sleeve thereabout and lace it up.
Some of these disadvantages are overcome by utilizing the pin-type locking means disclosed in U.S. Pat. No. 2,602,207, since the locking is accomplished more quickly; however, there are still some improvements necessary in such a cable grip. In particular, the rigid rod does not closely conform to the outer configuration of the cable, so that when under tension the radial compressive forces are restricted, thereby sometimes allowing the grip to slip. In addition, the rigid rod is not flexible so that it becomes extremely difficult to install onto a cable with any degree of curvature along its longitudinal axis. Because of the reduction in gripping ability due to the rigid rod, such cable grips are usually recommended for temporary or light duty use only.